preliminary question about upgrading switch on old 115VAC 1-ph motor - Woodworking Talk - Woodworkers Forum
 
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post #1 of 16 Old 07-03-2012, 09:14 PM Thread Starter
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preliminary question about upgrading switch on old 115VAC 1-ph motor

I bought an old 1950s era Delta Homecraft table saw with a single-phase 115VAC 12amp motor. I want to upgrade the on/off switch and ground the motor.

There's a little metal toggle switch on the side of the saw, and two-wire lamp cord leading from that switch to an array of two-prong outlets mounted on the back of the saw. A two-prong plug coming out of the motor plugs into one of those sockets on the back of the saw, and a longer cord emerging from the motor, also with a two-prong plug, gets plugged into the mains.

I would like to upgrade the little metal toggle switch with a new paddle switch like this one and upgrade the two-conductor wire to three-conductor wire, and ground the motor.

Will I end up with a single three-wire cord with a three-prong plug on it emerging from the motor, with the black wire going to the hot screw in the motor, the white/neutral wire going to the neutral screw in the motor, and green/ground going to a bolt on the motor's shell?

I can attach a picture tomorrow of the insides of the motor's electrical box.

Last edited by tim123; 07-03-2012 at 09:24 PM.
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post #2 of 16 Old 07-03-2012, 09:33 PM
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Pictures really help in the "remote" diagnosis.

Since you are already at 110V it is likely to find many options, but it helps to know the starting point.
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post #3 of 16 Old 07-04-2012, 08:08 AM Thread Starter
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Here is a picture of the electric box on the motor.

[1] long two-conductor cord that plugs into mains
[2] short two-conductor cord that plugs into switched outlet on saw (this outlet on the saw is "free-standing": lamp cord connects the outlet to the toggle switch but there are no other wires)
[3] the white wire of the short plug cord
[4] the white wire of the long mains plug cord
[5] the black wire of the long mains plug cord
[6] the black wire of the short plug cord
[7] bolt on the housing; no wire is connected to it
[8] this wire comes from inside the motor
[9] this wire comes from inside the motor


The two white neutral conductors [3] and [4] from the long cord to mains and the shot cord to the saw-mounted outlet are twisted together and taped.

The black conductor [5] from the mains cord connects to the lowest of the three studs [A].

The black conductor from the short cord [6] connects to the top stud [C].


No white wire appears to be connected to the motor.

The new paddle switch I bought has its own three-prong plug that goes to the mains, and a three-conductor outlet, as shown in the picture found at the link in my first post.

Is it possible to remove [1] and [2] completely, and introduce a three-conductor wire with a three-prong plug that would get plugged into the outlet on the new paddle switch? If so, which wire goes to which stud [A,B,C] and would the green ground wire go the the bolt [7] ?


Thanks very much for the help. I do not understand the wiring.
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Last edited by tim123; 07-04-2012 at 08:18 AM.
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post #4 of 16 Old 07-04-2012, 08:54 AM
where's my table saw?
 
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Tim if it were me ...

I would elmiinate the outlet on the motor circuit since you don't want any addition draw on that circuit from other tools or vacs etc.

I would get a double pole 120 V rated switch which means it breaks both the black and white/neutral wires at the same time.
So the 3 conductor wire from the wall plug comes into the switch box where the green is connected to the box as a ground and the black and white are the switched wires.
A switch like this:
http://www.grizzly.com/products/110-...f-Switch/H8243

Then a new 3 conductor wire goes to the motor and replaces all other cords. Black to the hot wire terminal, white to the neutral and green to a screw on the motor frame.

Lamp cord (18 GA ) has no place in a motor circuit. You need 14 GA wire or 12 GA wire depending on the Amperage draw on the motor plate....15 amps and greater should be fed with 12 GA wire. JMO.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #5 of 16 Old 07-04-2012, 09:10 AM
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There should be continuity between the box the switch is mounted to and throughout the saw including the motor. All I would do is install a 110V household light switch and a 12/2 with ground stranded wire. It is really recommended that a electric motor switch is used however common light switches last me for years. The green wire could just be attached to the switch box. The white wire would go directly to the motor and the black wire would be interrupted by the switch. If you wish to carry the green wire directly to the motor attach it to #7 on your illustration.
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post #6 of 16 Old 07-04-2012, 09:18 AM Thread Starter
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Thank you for the advice, woodnthings.

Which of the three terminals marked [A], [B], [C] in the picture is the hot and which is the neutral?

P.S. The lamp cord is something the previous owner rigged up! My ignorance runs deep, but not Marianas Trench deep
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post #7 of 16 Old 07-04-2012, 09:43 AM
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The best method to confirm which lead is hot is a multi-meter.

The wire colours are not common for the US. I am seeing green, black and blue.

In the US black is frequently hot, white is frequently neutral and green is frequently ground (or just bare copper) in a 110V circuit.

Since the colours are not the normal, the only way to confirm is a multi-meter.

If the other end of the cord has a plug which you can remove, you could use this to confirm.

With the middle (ground) pin pointing up, the hot lead is on the left and the neutral is on the right.
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post #8 of 16 Old 07-04-2012, 09:54 AM
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the hot is black from the plug

In "mains" wire No. 1 which goes to Terminal A, wire no. 5. The neutral is from the plug and goes to "taped" connection which is hard to see.
I would eliminate 2 conductor cord, No. 2, with wires No. 6 and 3, the free standing outlet. It may be wired such that when the motor starts the outlet becomes live to some reason a shop vac or lamp??


Where is the existing switch now...

Since the photos do NOT appear in a rely I may have to "edit" this after rechecking.....

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #9 of 16 Old 07-04-2012, 10:02 AM Thread Starter
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Thanks Dave. But I didn't follow. All of the wires are only two-conductor now. There is no middle pin.

If I were to turn the motor on as it is wired now, before making any changes, is there a way to use a multi-meter to determine which of those three terminals is the hot one and which is the neutral?

I've never used a multi-meter before. Is it possible to destroy the motor by touching the needles to the wrong combination of terminals?
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post #10 of 16 Old 07-04-2012, 10:06 AM Thread Starter
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Quote:
Originally Posted by woodnthings View Post
In "mains" wire No. 1 which goes to Terminal A, wire no. 5. The neutral is from the plug and goes to "taped" connection which is hard to see.
I would eliminate 2 conductor cord, No. 2, with wires No. 6 and 3, the free standing outlet. It may be wired such that when the motor starts the outlet becomes live to some reason a shop vac or lamp??


Where is the existing switch now...

Since the photos do NOT appear in a rely I may have to "edit" this after rechecking.....
What happens then to wire #4? It is now spliced to wire #3 and the two are taped. These two white wires connect only to each other, not to any terminal on the motor.

The toggle switch is mounted on the side of the saw. Simple little metal throw-switch wired up to the receptacle on the back of the saw.

Last edited by tim123; 07-04-2012 at 10:12 AM.
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post #11 of 16 Old 07-04-2012, 10:13 AM
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Quote:
Originally Posted by tim123 View Post
What happens then to wire #4? It is now spliced to wire #3 and the two are taped. These two white wires connect only to each other, not to any terminal on the motor.
In general in most circuits, white or neutral wires do get taped together. However, on a motor the white wire goes to the motor windings and there may not be a terminal as such. It would be unusual if there is no terminal for the white wire.

It's possible that through some quirk the white goes back through the accessory cord and then goes back to the green terminal.

Your best bet is to take the motor in to a shop and have them analyze the wiring.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #12 of 16 Old 07-04-2012, 10:22 AM Thread Starter
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Here are the toggle switch, the lamp cord connected to the toggle switch, and the bank of receptacles to which the lamp cord is connected. The cord #2 plugs into one of those receptacles.
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post #13 of 16 Old 07-04-2012, 10:33 AM Thread Starter
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Quote:
Originally Posted by woodnthings View Post
In general in most circuits, white or neutral wires do get taped together. However, on a motor the white wire goes to the motor windings and there may not be a terminal as such. It would be unusual if there is no terminal for the white wire.

It's possible that through some quirk the white goes back through the accessory cord and then goes back to the green terminal.

Your best bet is to take the motor in to a shop and have them analyze the wiring.
That the white wires were taped together and did not connect to the motor is the main source of my confusion here. wire #6 might actually be functioning as the neutral. It is coming back from those receptacles. The switch and lamp cord and receptacles are just a long extension of the white conductor #3 coming in from the mains on cord [1]. I think you're right about the "quirk".

Last edited by tim123; 07-04-2012 at 10:42 AM.
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post #14 of 16 Old 07-04-2012, 05:42 PM Thread Starter
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Confirming: C is neutral, A is hot. It's working, woohoo.
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post #15 of 16 Old 07-04-2012, 08:04 PM
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please ditch all that lamp cord wiiring

Just have your motor on the plug from the outlet, nothing else. It makes trouble shooting far easier and it will let the motor get all the current possible from the outlet. Practically speaking there should be only the motor on a table saw circuit, no other appliance, tools or lamps.
Shop lighting should always be on a separate circut for safety in the event your saw trips the breaker and all the lights are now out as well and you are fumbling around in a dark shop with sharp objects...... bill

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #16 of 16 Old 07-05-2012, 08:01 AM Thread Starter
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Quote:
Originally Posted by woodnthings View Post
Just have your motor on the plug from the outlet, nothing else. It makes trouble shooting far easier and it will let the motor get all the current possible from the outlet. Practically speaking there should be only the motor on a table saw circuit, no other appliance, tools or lamps.
Shop lighting should always be on a separate circut for safety in the event your saw trips the breaker and all the lights are now out as well and you are fumbling around in a dark shop with sharp objects...... bill
The previous owner's lamp cord is now history.
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